linux.git/include/linux/memcontrol.h, branch v7.1-rc2

mm: memcontrol: correct the nr_pages parameter type of mem_cgroup_update_lru_size()

2026-04-18T07:10:48+00:00

The nr_pages parameter of mem_cgroup_update_lru_size() represents a page
count.  During the reparenting of LRU folios, the value passed to it can
potentially exceed the maximum value of a 32-bit integer.  It should be
declared as long instead of int to match the types used in lruvec size
accounting and to prevent possible overflow.

Update the parameter type to long to ensure correctness.

Link: https://lore.kernel.org/fd4140de44fa0a3978e4e2426731187fe8625f0b.1774604356.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng 
Reviewed-by: Lorenzo Stoakes (Oracle) 
Reviewed-by: Harry Yoo (Oracle) 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: David Hildenbrand 
Cc: Hamza Mahfooz 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Johannes Weiner 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Muchun Song 
Cc: Roman Gushchin 
Cc: Shakeel Butt 
Cc: Usama Arif 
Cc: Wei Xu 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: memcontrol: eliminate the problem of dying memory cgroup for LRU folios

2026-04-18T07:10:47+00:00

Now that everything is set up, switch folio->memcg_data pointers to
objcgs, update the accessors, and execute reparenting on cgroup death.

Finally, folio->memcg_data of LRU folios and kmem folios will always point
to an object cgroup pointer.  The folio->memcg_data of slab folios will
point to an vector of object cgroups.

Link: https://lore.kernel.org/80cb7af198dc6f2173fe616d1207a4c315ece141.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Muchun Song 
Signed-off-by: Qi Zheng 
Acked-by: Shakeel Butt 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: Chengming Zhou 
Cc: Chen Ridong 
Cc: David Hildenbrand 
Cc: Hamza Mahfooz 
Cc: Harry Yoo 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Johannes Weiner 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nhat Pham 
Cc: Roman Gushchin 
Cc: Suren Baghdasaryan 
Cc: Usama Arif 
Cc: Vlastimil Babka 
Cc: Wei Xu 
Cc: Yosry Ahmed 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: memcontrol: convert objcg to be per-memcg per-node type

2026-04-18T07:10:47+00:00

Convert objcg to be per-memcg per-node type, so that when reparent LRU
folios later, we can hold the lru lock at the node level, thus avoiding
holding too many lru locks at once.

[zhengqi.arch@bytedance.com: reset pn->orig_objcg to NULL]
  Link: https://lore.kernel.org/20260309112939.31937-1-qi.zheng@linux.dev
[akpm@linux-foundation.org: fix comment typo, per Usama.  Reflow comment to 80 cols]
[devnexen@gmail.com: fix obj_cgroup leak in mem_cgroup_css_online() error path]
  Link: https://lore.kernel.org/20260322193631.45457-1-devnexen@gmail.com
[devnexen@gmail.com: add newline, per Qi Zheng]
  Link: https://lore.kernel.org/20260323063007.7783-1-devnexen@gmail.com
Link: https://lore.kernel.org/56c04b1c5d54f75ccdc12896df6c1ca35403ecc3.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng 
Signed-off-by: David Carlier 
Acked-by: Shakeel Butt 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: Chengming Zhou 
Cc: Chen Ridong 
Cc: David Hildenbrand 
Cc: Hamza Mahfooz 
Cc: Harry Yoo 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Johannes Weiner 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Muchun Song 
Cc: Nhat Pham 
Cc: Roman Gushchin 
Cc: Suren Baghdasaryan 
Cc: Usama Arif 
Cc: Vlastimil Babka 
Cc: Wei Xu 
Cc: Yosry Ahmed 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Cc: Usama Arif 
Signed-off-by: Andrew Morton

mm: memcontrol: prepare for reparenting LRU pages for lruvec lock

2026-04-18T07:10:46+00:00

The following diagram illustrates how to ensure the safety of the folio
lruvec lock when LRU folios undergo reparenting.

In the folio_lruvec_lock(folio) function:

    rcu_read_lock();
retry:
    lruvec = folio_lruvec(folio);
    /* There is a possibility of folio reparenting at this point. */
    spin_lock(&lruvec->lru_lock);
    if (unlikely(lruvec_memcg(lruvec) != folio_memcg(folio))) {
        /*
         * The wrong lruvec lock was acquired, and a retry is required.
         * This is because the folio resides on the parent memcg lruvec
         * list.
         */
        spin_unlock(&lruvec->lru_lock);
        goto retry;
    }

    /* Reaching here indicates that folio_memcg() is stable. */


In the memcg_reparent_objcgs(memcg) function:

    spin_lock(&lruvec->lru_lock);
    spin_lock(&lruvec_parent->lru_lock);
    /* Transfer folios from the lruvec list to the parent's. */
    spin_unlock(&lruvec_parent->lru_lock);
    spin_unlock(&lruvec->lru_lock);

After acquiring the lruvec lock, it is necessary to verify whether the
folio has been reparented.  If reparenting has occurred, the new lruvec
lock must be reacquired.  During the LRU folio reparenting process, the
lruvec lock will also be acquired (this will be implemented in a
subsequent patch).  Therefore, folio_memcg() remains unchanged while the
lruvec lock is held.

Given that lruvec_memcg(lruvec) is always equal to folio_memcg(folio)
after the lruvec lock is acquired, the lruvec_memcg_debug() check is
redundant.  Hence, it is removed.

This patch serves as a preparation for the reparenting of LRU folios.

Link: https://lore.kernel.org/23f22cbb1419f277a3483018b32158ae2b86c666.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Muchun Song 
Signed-off-by: Qi Zheng 
Acked-by: Johannes Weiner 
Acked-by: Shakeel Butt 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: Chengming Zhou 
Cc: Chen Ridong 
Cc: David Hildenbrand 
Cc: Hamza Mahfooz 
Cc: Harry Yoo 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nhat Pham 
Cc: Roman Gushchin 
Cc: Suren Baghdasaryan 
Cc: Usama Arif 
Cc: Vlastimil Babka 
Cc: Wei Xu 
Cc: Yosry Ahmed 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: do not open-code lruvec lock

2026-04-18T07:10:46+00:00

Now we have lruvec_unlock(), lruvec_unlock_irq() and
lruvec_unlock_irqrestore(), but no the paired lruvec_lock(),
lruvec_lock_irq() and lruvec_lock_irqsave().

There is currently no use case for lruvec_lock_irqsave(), so only
introduce lruvec_lock_irq(), and change all open-code places to use this
helper function.  This looks cleaner and prepares for reparenting LRU
pages, preventing user from missing RCU lock calls due to open-code lruvec
lock.

Link: https://lore.kernel.org/2d0bafe7564e17ece46dfd58197af22ce57017dc.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng 
Acked-by: Muchun Song 
Acked-by: Shakeel Butt 
Reviewed-by: Harry Yoo 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: Chengming Zhou 
Cc: Chen Ridong 
Cc: David Hildenbrand 
Cc: Hamza Mahfooz 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Johannes Weiner 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nhat Pham 
Cc: Roman Gushchin 
Cc: Suren Baghdasaryan 
Cc: Usama Arif 
Cc: Vlastimil Babka 
Cc: Wei Xu 
Cc: Yosry Ahmed 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: memcontrol: prevent memory cgroup release in count_memcg_folio_events()

2026-04-18T07:10:45+00:00

In the near future, a folio will no longer pin its corresponding memory
cgroup.  To ensure safety, it will only be appropriate to hold the rcu
read lock or acquire a reference to the memory cgroup returned by
folio_memcg(), thereby preventing it from being released.

In the current patch, the rcu read lock is employed to safeguard against
the release of the memory cgroup in count_memcg_folio_events().

This serves as a preparatory measure for the reparenting of the
LRU pages.

Link: https://lore.kernel.org/dea6aa0389367f7fd6b715c8837a2cf7506bd889.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Muchun Song 
Signed-off-by: Qi Zheng 
Reviewed-by: Harry Yoo 
Acked-by: Johannes Weiner 
Acked-by: Shakeel Butt 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: Chengming Zhou 
Cc: Chen Ridong 
Cc: David Hildenbrand 
Cc: Hamza Mahfooz 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nhat Pham 
Cc: Roman Gushchin 
Cc: Suren Baghdasaryan 
Cc: Usama Arif 
Cc: Vlastimil Babka 
Cc: Wei Xu 
Cc: Yosry Ahmed 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

writeback: prevent memory cgroup release in writeback module

2026-04-18T07:10:45+00:00

In the near future, a folio will no longer pin its corresponding memory
cgroup.  To ensure safety, it will only be appropriate to hold the rcu
read lock or acquire a reference to the memory cgroup returned by
folio_memcg(), thereby preventing it from being released.

In the current patch, the function get_mem_cgroup_css_from_folio() and the
rcu read lock are employed to safeguard against the release of the memory
cgroup.

This serves as a preparatory measure for the reparenting of the
LRU pages.

Link: https://lore.kernel.org/645f99bc344575417f67def3744f975596df2793.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Muchun Song 
Signed-off-by: Qi Zheng 
Reviewed-by: Harry Yoo 
Acked-by: Johannes Weiner 
Acked-by: Shakeel Butt 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: Chengming Zhou 
Cc: Chen Ridong 
Cc: David Hildenbrand 
Cc: Hamza Mahfooz 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nhat Pham 
Cc: Roman Gushchin 
Cc: Suren Baghdasaryan 
Cc: Usama Arif 
Cc: Vlastimil Babka 
Cc: Wei Xu 
Cc: Yosry Ahmed 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: memcontrol: return root object cgroup for root memory cgroup

2026-04-18T07:10:44+00:00

Memory cgroup functions such as get_mem_cgroup_from_folio() and
get_mem_cgroup_from_mm() return a valid memory cgroup pointer, even for
the root memory cgroup.  In contrast, the situation for object cgroups has
been different.

Previously, the root object cgroup couldn't be returned because it didn't
exist.  Now that a valid root object cgroup exists, for the sake of
consistency, it's necessary to align the behavior of object-cgroup-related
operations with that of memory cgroup APIs.

Link: https://lore.kernel.org/e9c3f40ba7681d9753372d4ee2ac7a0216848b95.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Muchun Song 
Signed-off-by: Qi Zheng 
Acked-by: Johannes Weiner 
Acked-by: Shakeel Butt 
Reviewed-by: Harry Yoo 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: Chengming Zhou 
Cc: Chen Ridong 
Cc: David Hildenbrand 
Cc: Hamza Mahfooz 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nhat Pham 
Cc: Roman Gushchin 
Cc: Suren Baghdasaryan 
Cc: Usama Arif 
Cc: Vlastimil Babka 
Cc: Wei Xu 
Cc: Yosry Ahmed 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: rename unlock_page_lruvec_irq and its variants

2026-04-18T07:10:44+00:00

It is inappropriate to use folio_lruvec_lock() variants in conjunction
with unlock_page_lruvec() variants, as this involves the inconsistent
operation of locking a folio while unlocking a page.  To rectify this, the
functions unlock_page_lruvec{_irq, _irqrestore} are renamed to
lruvec_unlock{_irq,_irqrestore}.

Link: https://lore.kernel.org/4e5e05271a250df4d1812e1832be65636a78c957.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Muchun Song 
Signed-off-by: Qi Zheng 
Acked-by: Roman Gushchin 
Acked-by: Johannes Weiner 
Reviewed-by: Harry Yoo 
Reviewed-by: Chen Ridong 
Acked-by: David Hildenbrand (Red Hat) 
Acked-by: Shakeel Butt 
Cc: Allen Pais 
Cc: Axel Rasmussen 
Cc: Baoquan He 
Cc: Chengming Zhou 
Cc: Hamza Mahfooz 
Cc: Hugh Dickins 
Cc: Imran Khan 
Cc: Kamalesh Babulal 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Michal Koutný 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nhat Pham 
Cc: Suren Baghdasaryan 
Cc: Usama Arif 
Cc: Vlastimil Babka 
Cc: Wei Xu 
Cc: Yosry Ahmed 
Cc: Yuanchu Xie 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: memcontrol: switch to native NR_VMALLOC vmstat counter

2026-04-05T20:53:04+00:00

Eliminates the custom memcg counter and results in a single, consolidated
accounting call in vmalloc code.

Link: https://lkml.kernel.org/r/20260223160147.3792777-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner 
Acked-by: Shakeel Butt 
Reviewed-by: Uladzislau Rezki (Sony) 
Reviewed-by: Roman Gushchin 
Reviewed-by: Vishal Moola (Oracle) 
Cc: Joshua Hahn 
Cc: Michal Hocko 
Cc: Muchun Song 
Cc: Shakeel Butt 
Signed-off-by: Andrew Morton